Sidewalk Fossils

Field Activities

Introduction to sidewalk fossils

The concrete of which sidewalks, and other structures, are made is
actually a kind of stone. To be exact, it is synthetic calcareous
conglomerate Synthetic means, " It is the real thing but
put together by human, rather than by natural, processes". Conglomerate
means, "A stone made of sediments of different sizes mixed
together, in this case, sand and gravel". Calcareous
means, "The
cement holding this stone together is calcium carbonate".

These activities may be done by groups of students on a field trip, or
individually on their own.

Leaf Fossils

Sometimes leaves or other objects fall into the concrete while it is
still wet, like mud. In the finishing process they may become
buried, partly buried, or merely pressed into the surface. As the
concrete is lithified (turned to stone), hardened, the impressions of
the objects become fossils. Just like natural fossils.

1. Draw a picture of each different kind of leaf. Include as many
details as you can, veins, leaf margins, stem. It may be
necessary to combine details from several fossils of the same kind
(just be sure they are the same kind).

2. Try to identify the kinds of plants the leaves came from. How
do you know? (Field guides to plants would be helpful.)

3. Search the area around the fossil location for plants (trees) with
leaves of the same kinds as the fossils.

4. Any other notes of interest.

Animal Track Fossils

It is not rare for animals to walk through wet concrete while it is
still wet and can take imprints, like wet mud. When the concrete,
or mud becomes lithified (hardened into rock) the foot prints become
fossils.

1. Draw a picture of each kind of print you find with as much detail as
you can.

2. Identify which prints are left, right, front, back. How do you
know?

3. Try to identify the animal which produced each kind of track. Cat?
Dog? Crow? Opossum? How do you know?
(Field guides to animals, or animal tracks would be
helpful.)

4. If the track is long enough, sketch the whole track. Which
direction was it going? Was it walking? Running? Hopping?
Or something else? How do you know?

5. Any other notes of interest.

Human Track Fossils

It is not rare for people (either accidentally or deliberately) to walk
through wet concrete while it is still wet and can take imprints, like
wet mud. When the concrete, or mud becomes lithified (hardened
into rock) the foot prints become fossils.

1. Draw a picture of each kind of print you find, include as much of
the pattern on the sole of a shoe as you can.

2. If it is a shoe print, what is the size of the shoe. Where did
you find a chart to convert shoe length to shoe size?

3. If the track is two steps or longer, sketch the whole track.
Which direction was the person going?

4. Was the person walking? Running? Something else? How do you
know?

5. Any other notes of interest.

Bicycle Track Fossils

It is not rare for people (either accidentally or deliberately) to ride
through wet concrete while it is still wet and can take imprints, like
wet mud. When the concrete, or mud becomes lithified (hardened
into rock) the wheel prints become fossils.

1. Draw the patterns of the treads of each tire with as much detail as
you can.

2. Sketch the entire track.

3. Identify the track of the front tire, and the track of the back
tire. How do you know?

4. Which direction was the bike going? How do you know?

5. How fast was the bike going? How do you know?

6. Any other notes of interest.

(To verify your hypotheses [ How do you know's] see the Lab Activity.)

Wheel Track Fossils

It is not rare for people (either accidentally or deliberately) to ride
through wet concrete while it is still wet and can take imprints, like
wet mud. When the concrete, or mud becomes lithified (hardened
into rock) the wheel prints become fossils.

1. Sketch the entire track.

2. Draw a section of the track with as much detail of each wheel as you
can find.

3. Which direction was it going? How do you know?

4. Identify the type of vehicle, skate, skate board, wagon, wheelchair,
etc. How do you know?